Best of luck to you. I gave up looking and made them myself, did a bit of a hack job but they work just fine. If you're handy with tools it's just a couple of cuts and bends in some 1/8" stainless or mild steel
(easier to find and work with, should be fine for 10+ years with a coat of paint), but getting the cuts and bends in the right place took me a few tries. If I were to do it again I would use some heavy cardstock to make templates first.